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2012 'water year' among driest ever seen in state

Oct 19, 2012 - Staff and wire reports

Only the 1988-89 and 1959-60 water years were drier, said Riverton meteorologist Jim Fahey.

Wyoming just completed its third-driest year in 118 years of statehood and saw its driest March through September period ever, the National Weather Service said Thursday.

Wyoming averaged 8.77 inches of snow and rain in the most recent measurement year, which ran from October 2010 to September.

Only the 1988-89 and 1959-60 water years were drier, said Jim Fahey, a weather service hydrologist in Riverton.

The dry year came after several wet years in Wyoming that included record snow packs in 2011 that brought widespread flooding to Fremont County for the second consecutive year.

Sharp contrast

Riverton has received 2.37 inches of measurable precipitation in 2012, just 28 percent of the 30-year average for this point in the calendar year. By Oct. 18 a year ago, Riverton had received 10.34 inches of precipitation.

Lander has received barely 5 inches so far, about half the typical amount through mid-October. Last year Lander had 13.32 inches through Oct. 18.

Fahey said the sharp change from one year to the next was highly unusual.

"In the last 20 years I haven't really seen that stark contrast ... as far as the numbers, in what we've seen last year and this year," Fahey said.

Widespread drought

Most of Wyoming is seeing drought conditions, with 98 percent of the state with at least moderate drought, according to the U.S. Drought Monitor. Fifty-seven percent of the state has either extreme or exceptional drought.

Fahey said the drought has sapped river basins and reservoirs.

Only the Upper Yellowstone River Basin in northwest Wyoming received normal precipitation over the past water year, he said. Most other basins received about 70 percent of normal rain and snow, while the Wind River Basin got just 64 percent for the October-through-September water year, and the Lower North Platte just 53 percent, Fahey said.

Reservoirs came through

Reservoirs that were brimming from last year's melted snow covered this year's irrigation demand despite the dry weather, he said.

Most of the reservoirs still have adequate water, but those in southeast Wyoming have been drawn down much more because of the drought and hot weather downstream in Nebraska.

"I think we can handle another dry year in the central and western part of Wyoming with our storage, but we're not looking too good in southeast Wyoming," he said.

Fahey said current predictions call for the drier-than-normal weather to continue through November. So far, long-term forecasts are unclear on how the winter will shape up because of uncertainty about development of an El Nino in the Pacific, he said.

Depending on its strength, an El Nino is thought to influence how much snow falls in certain areas of Wyoming during the winter.